1. Field of the Invention
The present invention relates to a pickup device mounted on an information recording medium playback device. More particularly, the invention relates to a pickup device for recording information into and reproducing the same from an information recording medium, such as CD (compact disk) or DVD (digital video disc, digital versatile disc).
2. Description of the Related Art
In the pickup device mounted on the information recording medium reproduction device, to accurately read information, which is optically recorded into an information recording medium, from the recording medium or to write information into the recording medium, an optical axis of the objective lens, which is for focusing a light beam emitted from a semiconductor laser as a light source on an information recording surface of the information recording medium, must be inclined at an appropriate angle with respect to the information recording surface.
For this reason, the pickup device is provided with a skew adjusting mechanism for adjusting an inclination of the optical axis of the objective lens in two directions, a radial direction and a tangential direction.
FIG. 8 is a side view showing a conventional pickup device is provided with the skew adjusting mechanism. A pickup device PU1 is formed with a lens holder 2 mounted on an objective lens 1, an actuator base 4 for supporting the lens holder 2 in a cantilever fashion by means of four 2-axes suspensions 3, which are equal in length, a plurality of adjusting screws 5 for adjusting an inclination of the actuator base 4, viz., an inclination of the optical axis of the objective lens 1, in a radial direction and a tangential direction, a pick-up case 6 for relatively slidably supporting the actuator base 4, and a pair of guide shafts 8 for supporting the pick-up case 6.
A protruded portion 4a having a part spherical surface is protruded from the lower surface of the actuator base 4 at a location, where the protruded portion 4a is supported in a recessed portion 6a formed in the pick-up case 6 while being slidable with the circumferential surface of the recessed portion 6a. Threaded holes 4b, while vertically passing through the pick-up case 6, are formed at predetermined positions closer to one end (the left side in the figure) of the actuator base 4. Those threaded holes 4b receive two adjusting screws 5 (one of which is omitted in the illustration), respectively. An urging-spring 7 is interposed between the other end (the right side in the figure) of the actuator base 4 and the pick-up case 6 such that it urges downwardly the other end of the actuator base 4.
In the skew mechanism thus constructed, the one end of the actuator base 4 with the objective lens 1 inserted therein is vertically adjusted by turning the adjusting screws 5, which pass through the pick-up case 6 and are threaded into the threaded holes 4b of the actuator base 4. By so doing, an inclination of the actuator base 4 to the pick-up case 6, viz., an inclination of the optical axis of the objective lens 1, is adjusted in the radial direction and the tangential direction so that the optical axis of the objective lens 1 is inclined at an appropriate angle with respect to an information recording surface of an information recording medium.
In the conventional pickup device PU1 thus constructed, it is necessary to separately manufacture the actuator base 4 and the pick-up case 6 in order to make a skew adjustment of the objective lens 1. Further, the number of parts, such as the adjusting screws 5 and the urging spring 7, which are to be assembled into the pickup device PU1, are increased. This results in increase of the size of the pickup device and increase of cost to manufacture the same. Further, the skew adjustment in which the actuator base 4 is biased in a desired direction while keeping the objective lens 1 in a floating state, is manually carried out by a skilled worker. As a result, the number of steps of manufacturing process is increased.
The present invention has been made to solve the problems of the conventional pickup device and has an object to reduce the number of component parts forming the pickup device and the size of the device, and to lighten the working load of the worker by simplifying the skew adjusting process.
To achieve the above object, there is provided a pickup device having a light source, an objective lens for converging rays of light emitted from the light source on a recording medium, a lens holder for holding the objective lens, and supporting means for movably supporting the lens holder.
The pickup device is improved in that a part of the objective lens and a part of the lens holder are movable relative to each other so as to adjust an inclination of an optical axis of the objective lens.
In the pickup device, a part of the objective lens and/or a part of the lens holder has a spherical surface.
Also, in the pickup device, the lens holder is provided with a contact portion which will be brought into contact with a manufacturing tool.